Fluorinated hydrogenated amorphous carbon films were grown by plasma-enhanced chemical vapor depositionŽPECVD.. Two sets of films were deposited. For the first set, the self-bias voltageŽVB.was kept constant and equal to 350 V, while the CF4 partial pressure in CH4CF4gas mixtures was changed from 0 to 80%. For the second one, a fixed 2:1 CF4CH4proportion in the precursor atmosphere was employed while VB was varied from 50 V to 500 V. The carbon chemical environment was investigated by X-ray photoelectron spectroscopyŽXPS., while structural changes in the carbon matrix were probed by Raman spectroscopy. The increase of both the CF4partial pressure and the VBleads to an increase of the fluorine concentration within the film. While in the first case the increase of the fluorine content leads to a relative increase of the CFn XPS bands, in the second one the relative intensity of the CFn bands are nearly the same within the range of VB values investigated. In particular, the CF2band grows for higher CF4partial pressures, while it is negligible in the self-bias study. The analysis of the Raman spectra shows that a progressive structural modification from a diamond-like towards a polymer-like material occurs for higher CF4partial pressures as well as for lower VB. This trend is accompanied by a noticeable broadening of the C1s XPS peak on the side of lower binding energies.
Fluorine incorporation into amorphous hydrogenated carbon films deposited by plasma-enhanced chemical vapor deposition: structural modifications investigated by X-ray photoelectron spectrometry and Raman spectroscopy
MARIOTTO, Gino;
2001-01-01
Abstract
Fluorinated hydrogenated amorphous carbon films were grown by plasma-enhanced chemical vapor depositionŽPECVD.. Two sets of films were deposited. For the first set, the self-bias voltageŽVB.was kept constant and equal to 350 V, while the CF4 partial pressure in CH4CF4gas mixtures was changed from 0 to 80%. For the second one, a fixed 2:1 CF4CH4proportion in the precursor atmosphere was employed while VB was varied from 50 V to 500 V. The carbon chemical environment was investigated by X-ray photoelectron spectroscopyŽXPS., while structural changes in the carbon matrix were probed by Raman spectroscopy. The increase of both the CF4partial pressure and the VBleads to an increase of the fluorine concentration within the film. While in the first case the increase of the fluorine content leads to a relative increase of the CFn XPS bands, in the second one the relative intensity of the CFn bands are nearly the same within the range of VB values investigated. In particular, the CF2band grows for higher CF4partial pressures, while it is negligible in the self-bias study. The analysis of the Raman spectra shows that a progressive structural modification from a diamond-like towards a polymer-like material occurs for higher CF4partial pressures as well as for lower VB. This trend is accompanied by a noticeable broadening of the C1s XPS peak on the side of lower binding energies.
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